AME 5 End of Unit

C. Cut out the delaminated section, fill the cavity with a core material, and then cover with a new layer of laminate.

• Explanation:
  1. Cut out the delaminated section: Removing the delaminated or damaged area ensures that all compromised material is eliminated, providing a clean surface for repair.
  2. Fill the cavity with a core material: In sandwich construction, the core material (like foam or balsa) provides structural integrity. Replacing the core material restores the strength and rigidity of the hull.
  3. Cover with a new layer of laminate: Applying a new layer of laminate over the repaired area integrates it back into the hull’s structure, reinforcing the repair and restoring the original strength.

Incorrect Answers:

A. Remove the damaged area, inject resin into the void, and then apply a new layer of fiberglass cloth over the repair.

• Why it's incorrect:
  1. Injecting resin into the void: While injecting resin can be effective for repairing small voids or blisters, it is not suitable for extensive delamination. In sandwich construction, merely injecting resin does not address the missing or damaged core material.
  2. Applying a new layer of fiberglass cloth: This approach does not replace the core material, which is crucial in sandwich construction. The structural integrity of the hull relies on the core material in addition to the laminate layers.

B. Sand the affected area, apply a primer coat, and then repaint the hull to seal the surface.

• Why it's incorrect:
  1. Sanding and repainting: This method only addresses surface issues and does not repair the internal delamination or restore the structural integrity of the hull. It is a cosmetic fix rather than a structural repair.

D. Drill holes into the delaminated area to allow moisture to escape, then apply a sealant and repaint the hull.

• Why it's incorrect:
  1. Drilling holes and applying sealant: This approach is more appropriate for addressing blisters rather than delamination. Drilling and sealing do not repair the internal structural damage caused by delamination. Like option B, this method is a superficial fix and does not address the core material or structural integrity of the hull.

Correct Answer:

C. Cut away the blistered area entirely, clean and dry the exposed surface, fill the void with a marine-grade filler, and then sand, prime, and repaint the area.

• Explanation: The proper procedure for treating a single osmotic blister involves removing the blistered area to expose the underlying void. Once the blister is cut away, the exposed surface must be thoroughly cleaned to remove any contaminants and dried completely to ensure that no moisture remains. After this, a marine-grade filler (such as an epoxy filler) is used to fill the void, restoring the hull's smooth surface. The area is then sanded to match the surrounding hull, primed to ensure good adhesion, and repainted to protect the repair. This method ensures that the blister is fully removed and the structural integrity of the hull is restored.

Incorrect Answers:

A. Sand the blister until it is flush with the surrounding hull, then apply a layer of antifouling paint to seal the area.

• Why it's incorrect: Simply sanding the blister flush with the hull does not address the underlying cause of the blister, which is the accumulation of fluid and pressure within the laminate. Without removing the blister and treating the void, the problem may reoccur or worsen. Additionally, applying antifouling paint does not adequately seal or repair the damaged area.

B. Drill a small hole into the blister to release the pressure, then fill the void with epoxy resin before sanding and repainting the area.

• Why it's incorrect: While drilling a hole might relieve pressure temporarily, it does not fully remove the damaged laminate or the contaminants within the blister. This method can leave weakened areas in the hull and might not effectively prevent the blister from reforming. The best practice is to remove the blister entirely rather than just draining it.

D. Heat the blister with a blowtorch until it deflates, then apply a layer of fiberglass cloth over the area to reinforce the hull.

• Why it's incorrect: Using heat to deflate the blister is not a recommended practice and could cause further damage to the GRP laminate. Heat can weaken the resin and the fiberglass structure, leading to larger issues. Additionally, applying fiberglass cloth over the blister without removing the damaged material does not properly address the underlying problem and may lead to further blistering or structural weaknesses.

Correct Answer:

A. Tapping the hull with a metal hammer to listen for changes in sound and using a moisture meter to measure the moisture content.

• Explanation:
  1. Tapping the hull with a metal hammer: This technique, known as "sounding," involves tapping the hull with a hammer to listen for changes in sound. A solid, healthy hull will produce a consistent, clear sound, whereas areas with delamination may produce a dull or hollow sound. This method helps identify areas where the laminate may be separating.
  2. Using a moisture meter: Moisture meters are effective tools for detecting the presence of moisture within the laminate. High moisture readings in specific areas can indicate that water has penetrated the laminate and is contributing to delamination. This method helps locate areas where moisture may have caused structural issues.

Incorrect Answers:

B. Inspecting for surface cracks and applying a UV light to detect underlying damage.

• Why it's incorrect:
  1. Inspecting for surface cracks: While surface cracks can indicate problems, they do not specifically detect delamination. Delamination occurs internally within the laminate and may not always be visible on the surface.
  2. Applying a UV light: UV light is typically used to detect issues with cured resins or surface coatings, but it is not effective for detecting internal delamination or moisture content.

C. Conducting a visual inspection for color changes and using a thermal camera to detect temperature variations.

• Why it's incorrect:
  1. Visual inspection for color changes: Color changes on the surface might indicate cosmetic issues but do not reliably detect internal delamination. Delamination often occurs beneath the surface and may not cause visible color changes.
  2. Using a thermal camera: Thermal cameras detect temperature variations and are useful for identifying heat-related issues, but they are not typically effective for detecting internal delamination or moisture within the laminate.

D. Measuring the thickness of the hull with a caliper and checking for vibrations when the hull is exposed to high winds.

• Why it's incorrect:
  1. Measuring hull thickness with a caliper: Thickness measurements may not reveal internal delamination since the outer thickness might remain unchanged even if there is separation between layers inside.
  2. Checking for vibrations in high winds: Vibrations caused by wind do not provide information about internal delamination. Delamination is better detected through methods that reveal internal damage or moisture, such as tapping and moisture meters.

Correct Answer:

A. The keel and the areas around the bilge.

• Explanation:
  1. Keel: The keel area is often the most exposed part of the hull to water, making it more susceptible to osmotic blisters. The constant contact with water and potential for damage or wear in this area increase the risk of moisture ingress.
  2. Areas around the bilge: These areas are prone to moisture accumulation due to water ingress and drainage, which can contribute to osmotic blistering. The bilge area is also where water often collects and where hull damage is more common, leading to increased risk of blisters.

Incorrect Answers:

B. The stern and the transom.

• Why it's incorrect:
  1. Stern: While the stern and transom can be exposed to water, they are less commonly affected by osmotic blisters compared to the keel and bilge areas. The stern area is typically less in contact with water over time compared to the keel.
  2. Transom: The transom is generally less susceptible to osmotic blisters because it is not as frequently immersed in water as other parts of the hull, particularly the keel.

C. The bow and the waterline area.

• Why it's incorrect:
  1. Bow: Although the bow is submerged and exposed to water, osmotic blisters are more commonly found in areas like the keel and bilge where water is more consistently in contact with the hull.
  2. Waterline area: The waterline area can be affected by blisters but is less commonly affected compared to the keel and bilge areas. Blisters are more prevalent where water exposure is more direct and prolonged.

D. The midship section and areas around the strakes.

• Why it's incorrect:
  1. Midship section: This area is less commonly affected by osmotic blisters compared to the keel and bilge. The midship section is not in constant contact with water like the keel is.
  2. Areas around the strakes: Strakes are structural features that can be affected by various forms of damage, but osmotic blisters are typically more common in areas like the keel and bilge where moisture exposure is more direct.

Correct Answer:

A. Reapply a new gelcoat layer and perform a thorough inspection to ensure UV protection.

• Explanation:
  1. Reapply a new gelcoat layer: Since root whitening is caused by the degradation of the existing gelcoat due to UV exposure, applying a new gelcoat layer can restore the protective barrier and improve the hull's appearance.
  2. Perform a thorough inspection to ensure UV protection: Ensuring proper UV protection involves checking that the gelcoat is adequately applied and considering future protective measures to prevent further degradation, such as applying UV-resistant coatings.

Incorrect Answers:

B. Increase the anti-fouling coating thickness and improve hull ventilation.

• Why it's incorrect:
  1. Increase anti-fouling coating thickness: Anti-fouling coatings are used to prevent marine growth and do not address the root cause of root whitening, which is related to UV degradation of the gelcoat.
  2. Improve hull ventilation: While ventilation is important for preventing moisture issues, it does not directly address root whitening, which is primarily caused by UV exposure and gelcoat degradation.

C. Apply a fresh layer of sealant and inspect the hull for moisture ingress.

• Why it's incorrect:
  1. Apply a fresh layer of sealant: Sealants are used to seal joints and fittings, but they do not resolve root whitening. Root whitening involves the gelcoat layer, not sealants.
  2. Inspect for moisture ingress: While inspecting for moisture ingress is important for other issues, it does not directly address the UV degradation of the gelcoat that causes root whitening.

D. Replace the laminate layers and adjust the hull shape for better load distribution.

• Why it's incorrect:
  1. Replace the laminate layers: This action is excessive for addressing root whitening. The issue is with the gelcoat layer, not the laminate layers.
  2. Adjust the hull shape: Changing the hull shape affects structural and performance characteristics but does not address the cosmetic issue of root whitening caused by UV exposure.

Correct Answer: B) By creating a continuous, void-free barrier with improved fiber-to-resin ratio that reduces water absorption.

• Explanation: Resin infusion molding creates a more consistent and continuous laminate with fewer voids compared to traditional methods. The reduced voids and better fiber-to-resin ratio create a more effective barrier against water penetration. This minimizes the potential for osmosis, where water gets trapped within the laminate and causes damage over time.

Incorrect Options:

A) By using a high-temperature curing process that melts any residual moisture in the composite.

• Explanation: Resin infusion molding does not involve high-temperature curing that melts moisture. Instead, it uses vacuum pressure to ensure that the resin infuses completely and evenly into the fabric, thereby reducing voids. Excess moisture is not "melted" but rather prevented by minimizing voids during the infusion process.

C) By applying a gel coat on the outer surface that acts as a sacrificial layer to prevent water ingress.

• Explanation: While applying a gel coat can help prevent water ingress to some extent, it is not specific to the resin infusion process itself. Gel coats are an additional step and are used in conjunction with various construction methods. The primary advantage of resin infusion is in creating a more consistent, void-free laminate, not just relying on an outer gel coat.

D) By using pre-formed glass fiber sheets that are already pre-treated to resist water penetration.

• Explanation: Pre-formed glass fiber sheets might be used in other methods, but resin infusion involves laying dry fibers into the mold and then infusing resin. The process is not about using pre-treated sheets but about achieving a thorough and consistent infusion that minimizes voids, thereby reducing the risk of osmosis.

Correct Answer: B) Laying down multiple layers of glass fiber mat and resin in a mold, followed by a curing process, with each layer being hand-rolled to remove air bubbles.

• Explanation: The traditional method for laying up a GRP hull involves placing multiple layers of glass fiber mat (or cloth) into a mold, applying resin to each layer, and then hand-rolling the layers to ensure good resin penetration and remove air bubbles. This process builds up the hull's strength and structural integrity. After the layers are applied, the hull is cured, usually at room temperature or with heat to set the resin.

Incorrect Options:

A) Applying a single layer of glass fiber and resin using a vacuum bagging technique to ensure even distribution.

• Explanation: While vacuum bagging is a technique used in advanced composites to remove air and ensure even resin distribution, it is not the traditional method for GRP hull construction. Traditional GRP layup generally involves hand-laying multiple layers and rolling them out, rather than using vacuum bagging.

C) Spraying a mixture of glass fiber and resin onto the mold using a high-pressure spray gun for a quick and even application.

• Explanation: This describes the chopper gun method, which is not the traditional hand layup method. The chopper gun is a more modern technique used for faster application but is different from the traditional hand-layup process that involves layering and hand-rolling.

D) Inserting pre-formed glass fiber and resin sheets into a mold and heating them to set the shape.

• Explanation: This describes a process similar to pre-preg layup methods or sheet molding compound (SMC), which is not traditional for GRP hulls. Traditional GRP hulls involve applying multiple layers of glass fiber and resin separately and curing them in the mold rather than using pre-formed sheets.

Correct Answer:

A. Excessive moisture ingress, poor adhesion between laminate layers, and impact damage.

• Explanation:
  1. Excessive moisture ingress: Moisture can penetrate the GRP laminate, leading to osmotic blistering. The pressure from the trapped moisture can cause the laminate layers to separate, resulting in delamination.
  2. Poor adhesion between laminate layers: If the resin used in the laminate does not properly bond with the fiberglass layers, it can result in weak spots. These weak areas are prone to separating under stress or pressure, leading to delamination.
  3. Impact damage: Physical impacts can cause cracks and damage to the GRP laminate. This damage can compromise the bond between layers, leading to delamination.

Incorrect Answers:

B. Overexposure to sunlight, improper curing of resin, and mechanical stress during fabrication.

• Why it's incorrect:
  1. Overexposure to sunlight: While UV damage can degrade the gelcoat and resin surface, it is not a direct cause of delamination. Sunlight can lead to surface degradation but does not typically cause the laminate layers to separate internally.
  2. Improper curing of resin: While improper curing can lead to weak bonds, it's not as direct a cause of delamination as poor adhesion between laminate layers. Curing issues more commonly result in surface defects or weak spots rather than full-scale delamination.
  3. Mechanical stress during fabrication: Mechanical stress during fabrication might affect the final product, but it is less likely to be a direct cause of delamination compared to factors like moisture ingress or impact damage.

C. Inadequate paint application, high temperatures during service, and contamination during manufacturing.

• Why it's incorrect:
  1. Inadequate paint application: Poor paint application affects only the outer surface of the hull. It doesn’t directly cause delamination of the internal laminate layers.
  2. High temperatures during service: While high temperatures can affect the performance of GRP, they are more likely to cause thermal expansion issues rather than direct delamination.
  3. Contamination during manufacturing: Contamination can affect the bond and quality of the laminate but is not typically a primary cause of delamination compared to moisture ingress and poor adhesion.

D. Vibrations from onboard machinery, excessive cleaning with harsh chemicals, and poor design of hull shape.

• Why it's incorrect:
  1. Vibrations from onboard machinery: Vibrations can cause wear and tear but are not a primary cause of delamination. Structural integrity issues are more often linked to moisture and impact damage.
  2. Excessive cleaning with harsh chemicals: While harsh chemicals can damage the surface, they are not a typical cause of delamination. Delamination is more related to internal issues within the laminate.
  3. Poor design of hull shape: Poor design might lead to other problems, but delamination is more directly related to internal bonding issues and moisture ingress.

Correct Answer: B) Placing dry glass fiber fabric in a mold, sealing the mold, and then injecting resin under vacuum pressure to infuse the fabric and cure the composite.

• Explanation: Resin infusion molding involves placing dry glass fiber fabric into a mold. The mold is then sealed, and resin is injected under vacuum pressure. This process ensures that the resin thoroughly infuses the fabric, creating a composite with uniform properties. The vacuum helps remove air bubbles and ensures a consistent resin distribution, which improves the strength and quality of the final product.

Incorrect Options:

A) Applying resin directly to layers of glass fiber mat in a mold, followed by hand-rolling to remove air bubbles and ensure even distribution.

• Explanation: This describes the hand lay-up method, not resin infusion molding. In hand lay-up, resin is manually applied to glass fiber layers, and hand-rolling is used to remove air bubbles. This process is different from resin infusion, which involves vacuum pressure to infuse the resin.

C) Spraying a mixture of glass fiber and resin onto the mold surface using a high-pressure spray gun, followed by curing at room temperature.

• Explanation: This describes the chopper gun method, which is used for spray-up applications rather than resin infusion molding. In spray-up, a mixture of glass fiber and resin is applied to the mold surface, which is different from the infusion process where dry fabric is used and resin is injected under vacuum.

D) Laying pre-formed sheets of glass fiber and resin in the mold and using heat to bond them together.

• Explanation: This describes a process similar to pre-preg lay-up or sheet molding compound (SMC), where pre-formed sheets are used and heat is applied to bond them. This is not the same as resin infusion molding, where dry fiber is used and resin is infused under vacuum.

Correct Answer:

A. Prolonged exposure to ultraviolet (UV) light and degradation of the gelcoat layer due to environmental conditions.

• Explanation:
  1. Prolonged exposure to UV light: The gelcoat layer of a GRP hull is directly exposed to sunlight, which contains UV rays. Over time, UV exposure breaks down the gelcoat, causing it to lose color and become discolored or faded, which is known as root whitening.
  2. Degradation of the gelcoat layer: Environmental conditions such as UV radiation, moisture, and temperature fluctuations contribute to the deterioration of the gelcoat layer. As the gelcoat degrades, it becomes more prone to discoloration, resulting in root whitening.

Incorrect Answers:

B. Excessive use of anti-fouling coatings and inadequate ventilation during construction.

• Why it's incorrect:
  1. Excessive use of anti-fouling coatings: Anti-fouling coatings are used to prevent marine growth and are not related to root whitening. They do not cause the gelcoat to degrade or change color.
  2. Inadequate ventilation during construction: While poor ventilation can affect the curing process, it does not directly cause root whitening. Root whitening is more related to UV exposure and environmental degradation of the gelcoat.

C. Improper application of sealants and excessive moisture ingress in the hull.

• Why it's incorrect:
  1. Improper application of sealants: Sealants are used to seal joints and fittings but do not cause root whitening. Root whitening involves the degradation of the gelcoat layer, not issues with sealants.
  2. Excessive moisture ingress: Moisture ingress can lead to problems such as osmotic blisters or delamination but is not directly related to root whitening, which is caused by UV exposure and environmental conditions.

D. Low-quality resin used in the laminate and high ambient temperatures during curing.

• Why it's incorrect:
  1. Low-quality resin: Low-quality resin affects the overall strength and durability of the laminate but does not specifically cause root whitening. Root whitening is related to the degradation of the gelcoat layer, not the resin used in the laminate.
  2. High ambient temperatures during curing: While temperature can impact curing, root whitening is primarily caused by UV degradation of the gelcoat layer rather than the curing process itself.

Correct Answer:

C. Measuring the moisture content of the hull using a moisture meter and looking for raised, soft, or discolored areas that may indicate osmotic blistering.

• Explanation: Osmosis in GRP hulls typically leads to the formation of blisters due to the accumulation of water within the laminate. The most effective way to detect osmosis is by using a moisture meter to measure the moisture content of the hull. High moisture readings in specific areas can indicate that water has penetrated the laminate, a sign of osmosis. Additionally, physical inspection for raised, soft, or discolored areas on the hull's surface is crucial, as these are typical indicators of osmotic blistering. Combining these methods provides a reliable way to identify the presence of osmosis before severe damage occurs.

Incorrect Answers:

A. Tapping the hull with a metal hammer to listen for changes in sound that indicate voids or blisters.

• Why it's incorrect: Tapping the hull with a hammer, known as "sounding," is a technique often used to detect delamination or voids in solid materials, like metal or wood. However, this method is less effective in detecting osmosis within a GRP laminate because the early stages of osmosis might not create noticeable changes in sound. Osmosis-related blisters are often filled with liquid, which may not produce a distinct sound difference when tapped.

B. Visually inspecting the hull for small cracks or surface scratches that may indicate underlying osmosis.

• Why it's incorrect: While visual inspection is an important part of hull maintenance, small cracks or surface scratches are not specific indicators of osmosis. These defects might result from other issues like impact damage or wear and tear, rather than osmosis. Osmotic blisters often appear as raised, soft, or discolored areas rather than simple cracks or scratches, so relying solely on visual inspection without considering these signs could lead to a missed diagnosis.

D. Applying pressure to the hull with a heavy object to see if the surface deforms, which could suggest the presence of osmosis.

• Why it's incorrect: Applying pressure to the hull to check for deformation is not a recommended method for detecting osmosis. This approach could cause further damage to the hull, especially if there is already structural weakness due to osmosis. Osmotic blisters may not necessarily cause visible deformation under pressure; instead, they are better identified by their raised, soft nature, and high moisture content, which are more safely and accurately detected using other methods like those described in the correct answer.

Correct Answer:

A. Inadequate gelcoat thickness, high moisture content in the hull, and poor bonding between laminate layers.

• Explanation:
  1. Inadequate gelcoat thickness: The gelcoat acts as a barrier to moisture ingress. If it is too thin or improperly applied, moisture can penetrate through to the laminate layers, leading to osmotic blistering.
  2. High moisture content in the hull: Moisture ingress into the laminate layers causes osmotic blistering. When water is trapped within the laminate, it creates pressure and forms blisters in the gelcoat.
  3. Poor bonding between laminate layers: If the bond between the laminate layers is weak, moisture can infiltrate the layers more easily, leading to the formation of osmotic blisters. Proper bonding is crucial for preventing moisture-related damage.

Incorrect Answers:

B. Excessive paint thickness, incorrect hull shape, and poor surface cleaning.

• Why it's incorrect:
  1. Excessive paint thickness: While excessive paint thickness can affect the hull’s appearance and performance, it does not directly cause osmotic blisters. Osmosis is more related to the laminate layers and moisture ingress rather than paint.
  2. Incorrect hull shape: Hull shape issues can affect performance and structural integrity but do not directly cause osmotic blisters, which are more related to moisture penetration and laminate issues.
  3. Poor surface cleaning: Poor cleaning can affect adhesion and aesthetics but does not directly contribute to the formation of osmotic blisters, which are primarily caused by moisture infiltration and laminate issues.

C. Excessive use of anti-fouling coatings, improper adhesive application, and high ambient temperatures during construction.

• Why it's incorrect:
  1. Excessive use of anti-fouling coatings: Anti-fouling coatings are used to prevent marine growth and do not cause osmotic blisters. They can impact the surface but are not a direct cause of osmotic issues.
  2. Improper adhesive application: Adhesive application issues are more related to bonding materials rather than causing osmotic blisters. Osmotic blisters result from moisture infiltration within the laminate.
  3. High ambient temperatures during construction: While high temperatures can affect curing, they are not a direct cause of osmotic blisters. Osmosis is related to moisture ingress and gelcoat issues rather than temperature alone.

D. Frequent washing with harsh chemicals, inadequate hull ventilation, and incorrect storage conditions.

• Why it's incorrect:
  1. Frequent washing with harsh chemicals: This can damage the surface but does not directly lead to osmotic blisters, which are caused by moisture penetrating the laminate.
  2. Inadequate hull ventilation: Poor ventilation can lead to moisture buildup but is not as directly linked to osmotic blisters as the other factors listed in option A.
  3. Incorrect storage conditions: While storage conditions can affect the overall condition of the hull, osmotic blisters are primarily related to moisture ingress through the laminate and gelcoat rather than storage alone.